We can get very small uncertainties in \(\gamma \)  because the uncertainties of the measured parameters are very small, especially for A0620-00. The uncertain factor \(\xi (\sigma )\)  would only change the resulting spike index slightly. Generally speaking, our results may suggest a possible evidence of the existence of dark matter density spike surrounding a black hole. It also suggests that a dark matter density spike might exist around a stellar-mass black hole (\(M_{\rm BH} \sim 1-10M_{\odot }\) ), but not only around a supermassive black hole [1]}, [2]}, [3]}, [4]} or an intermediate-mass black hole [5]}, [6]}, [7]} as suggested in the past literature. Since no previous study has focused on the case of dark matter density spike around a stellar-mass black hole, the effect of dark matter dynamical friction has also been neglected. In fact, one recent study has proposed that the electron excess detected by the DAMPE experiment might originate from the annihilating dark matter density spike in A0620-00 [8]}. Therefore, analyzing the effect of dark matter dynamical friction in BH-LMXBs would open a new independent way for investigating the dark matter distribution near stellar-mass black holes.
